如何通过密钥名称从mongoDB中检索值？ [英] How to retrieve a value from mongoDB, by its key name?

问题描述

我是mongoDB的新手。我正在使用java和mongoDB。我有一个json，

I am new to mongoDB. I am using java and mongoDB. I have a json like,

[{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "AA" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"},
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}]

    [{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "AA" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"},
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}]

    [{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "BB" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"},
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}]

    [{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "BB" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"},
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}]

在集合中所有文档 s有不同的 HomeTown ，我只知道密钥名称 HomeTown ，我怎么能得到 HomeTown 值？

In a collection all doc's have different HomeTown, i just know the key name HomeTown, how can i get the HomeTown values?

在mongo网站中，我只能找到 find（）和 findOne（）。

In mongo site, i just can find find() and findOne().

谢谢！

推荐答案

find（ ）就足够了。

db.CollectionName.find({},{HomeTown:1})

在java中，它将是：

in java, it would be:

BasicDBObject query = new BasicDBObject();
BasicDBObject field = new BasicDBObject();
field.put("HomeTown", 1);
DBCursor cursor = db.getCollection(collectionName).find(query,field);
while (cursor.hasNext()) {
    BasicDBObject obj = (BasicDBObject) cursor.next();
    result.add(obj.getString("HomeTown"));
}

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